A flush toilet or water closet (hereinafter WC) is a toilet that disposes of the waste products by using water to sweep them away down a drainpipe. The water is also used as a hygienic barrier between the drainpipe and the user.
As is with many inventions, the flush toilet did not suddenly spring into existence, but was the result of a long chain of minor improvements. From as early as 2600 BC, there are remains of flushing toilets, both private and communal, from several ancient civilizations around the world. In 1596 Sir John Harrington is said to have invented a flush toilet, ‘The Ajax’, for Elizabeth I of England. His design was ridiculed in England, but was adopted in France under the name Angrez. The design had a flush valve to let water out of the tank, and a wash-down design to empty the bowl. In 1775 Alexander Cummings invented the S-trap (British patent no. 814), still used today, that used standing water to seal the outlet of the bowl preventing the escape of foul air from the sewer. His design had a sliding valve in the bowl outlet above the trap. In 1777 Samuel Prosser invented and patented the ‘plunger closet’. In 1778 Joseph Bramah invented a hinged valve or ‘crank valve’ that sealed the bottom of the bowl, and a float valve system for the flush tank. His design was used mainly on boats. In 1819 Albert Giblin received British patent 4990 for the “Silent Valveless Water Waste Preventer”, a siphon discharge system. In 1852 J. G. Jennings invented a wash-out design with a shallow pan emptying into an S-trap. In 1857 the first American patent for a toilet, the ‘plunger closet’, was granted. In the 1880s Thomas Crapper's plumbing company built flush toilets of Giblin's design. After the company received a royal warrant, Crapper's name became synonymous with flush toilets. Although not the original inventor, Crapper popularized the siphon system for emptying the tank, replacing the earlier floating valve system which was prone to leaks; the similarity between Crapper's name and the much older word crap is merely a coincidence. In 1885 Thomas Twyford built the first one-piece china toilet using the flush-out siphon design by J. G. Jennings, similar to toilets used in today's society. In 1886 an early jet flush toilet was manufactured by the Beaufort Works in Chelsea, England.
The bowl, or pan, of a flush toilet is the receptacle into which waste is excreted, usually made of vitreous china, but sometimes made of stainless steel or composite plastics. Flush toilet bowls may be pedestal (free-standing), cantilever (wall-hung) or squat in design. There are several types of pans in common use: washdown, washout and siphon are just but a few. In less common use is the valve closet.
Washdown flush toilets are the simplest in design. They take the form of a ‘funnel’ shape, with a broad opening at the top narrowing to a smaller outlet connected to a drain. The pan usually incorporates a water trap at the base to seal the open end of the pan from the sewer. Washdown pans have almost vertical surfaces at the back of the pan and more gently sloping fronts to allow the outlet of the pan to be directly beneath the anus of a seated user to prevent soiling of the bowl. Washout pans have a shallow pool of water into which waste is excreted. Waste is cleared from the pan by being swept over a weir and into a drain by water from the flush.
The bowl of a flush toilet is a porcelain vessel; in North America this often has a built-in siphon, usually visible as a curved pipe protruding from the back. Normally, the bowl contains a small amount of water which is enough to form an air trap inside the siphon pipe, preventing foul air escaping from the sewer. When the toilet is used, liquid flows slowly through the siphon pipe as waste matter is added, but the flow volume is too small to fill the siphon. To flush the toilet, the user activates a flushing mechanism, which pours a large quantity of water quickly into the bowl. This creates a flow large enough to fill the siphon tube, causing the bowl to empty rapidly due to the weight of liquid in the tube. The flow stops when the liquid level in the bowl drops below the first bend of the siphon, allowing air to enter which breaks the column of liquid.
The earliest type of flush toilet, the valve closet is now scarce. More complicated in design than other water closets, reliability is lower and maintenance more difficult. The most common use for valve closets is now in portable closets for caravans and camping. The valve closet has a valve or flap at the exit of the bowl with a water-tight seal to retain a pool of water in the pan. When the flush toilet is flushed, the valve is opened and the water in the pan flows rapidly out of the bowl into the drains, carrying the waste with it.
Toilet bowls of today use different types of flush mechanisms. Retrofit direct flush installation in which the flushometer has been replaced with a sensor-operated system that automatically flushes the fixture when a user departs. The system uses an infrared proximity sensor to detect a user approaching the fixture, then it waits until the user departs. A solenoid is used to actuate the flush from a 6 volt battery, or the like, inside the unit that also powers the sensor circuit.
Another type of flush mechanism is the flushometer, or more commonly known as ‘direct flush’. In the old-style manual flush systems, the user presses a button, which opens a flush valve allowing mains-pressure water to flow into the bowl, or sometimes the user presses directly on a flush lever (a handle connected directly to a flushometer). The valve contains a pneumatic mechanism that closes it after a preset time. This system requires no storage tank, but requires high volume water for a very brief time period. Thus a ¾ inch (19 mm) pipe at minimum, and preferably a 1 inch (25 mm) pipe, but the high volume is used only for a short duration so very little water is used for the amount of flushing efficacy delivered. Direct valves are regulated by a device called a “flushometer” that meters out a certain controlled amount of water per flush. Direct flush makes the most efficient use of water, because it uses the water at full pressure and volume. The ability of water to perform the work in removing waste matter from the toilet bowl is given by pressure multiplied by volume. Typical pressure in an urban commercial building where flushometers are usually used is around 60 pounds per square inch (400 kPa) which is enough pressure to raise the water 137 feet (42 m) above the toilet bowl. Thus, in some sense, the effectiveness of direct flush is like having the tank 137 feet (42 m) above the bowl (lots of “flush energy”).
Flushometer type toilets are much more common in commercial installations (at least in the US); they're almost never seen in residential installations, except for dormitory and barracks areas. The installation of large numbers of toilets in buildings like sports stadiums has led to a test which is commonly performed before the final release of such a project, which is called “The Flush”. It entails stationing individuals in each restroom in the facility—in large installations this can amount to 100-400 people—and cueing them all by radio to flush their toilets as close to simultaneously as possible. The purpose of the test is twofold: it checks that the plumbing design engineers got their sums right on the sizes of both the main water supply to the building, and also the size of the drain piping. The test is commonly not made public before it happens, so as to avoid embarrassment if fails.
Still another type of flush mechanism is the valve tank type. A storage tank, or cistern, collects between 6 and 9 litres of water over a period of time. This system is suitable for locations plumbed with smaller diameter pipes. The storage tank is kept full by a float valve or ball cock. An outlet in the bottom of the tank is covered by a buoyant plastic cover (the flush valve) which is held in place by water pressure. To flush the toilet, the user pushes a lever, which lifts the flush valve from the outlet. The valve then floats clear of the outlet, allowing the tank to empty quickly into the bowl. As the water level drops, the floating flush valve descends back to the bottom of the tank and covers the outlet pipe again; this system is common in the USA. Tank type toilets waste the energy in the water by converting the potential energy of 137 feet (42 m) (the “head” of pressure in typical city water mains) times acceleration due to gravity, into around 18 inches (460 mm) above the bowl. Some older style toilets mitigate this waste of energy to some degree by having the tank be as high as possible (up near the bathroom ceiling), but modern tank type toilets waste the energy in the water, and therefore either use more water than necessary for a given flushing job, or for the same amount of water, flush less effectively than direct flush.
The valveless siphon tank type, this system, invented by Albert Giblin and common in the UK, uses a storage tank similar to that used in the flush valve system above. The user pushes a lever or button, forcing the water up into a siphon (not to be confused with the bowl siphon) which empties the entire tank into the bowl. The advantage of a siphon over the flush valve is that is has no sealing washers that can wear out and cause leaks, so it is favoured in places where there is a need to conserve water. Until recently the use of siphon-type cisterns was mandatory in the UK to avoid the potential waste of water by millions of leaking toilets. Older installations used a high-level cistern, or high suite, fitted above head height, that was operated by pulling a chain hanging down from a lever attached to the cistern. Some people still refer to the act of flushing a toilet (even a new low-cistern, or low suite, type) as “pulling the chain” or “flushing the chain”. Modern versions have a neater-looking low-level cistern with a lever that the user can reach directly, or a ‘close-coupled’ cistern that is even lower down and integrated with the bowl. This lower level results in loss of potential energy in the water, as the potential energy of water pressure is converted to the potential energy of height in a less advantageous manner, due to very little height, as described above.
Another type of toilet flush mechanism is the “pressure assist”, not uncommon in the United States, this system (invented by Bruce Martin) uses the water pressure within a structure to compress air within a closed vessel located within the vitreous enclosure. When flushed, the compressed air pushes into the bowl at a velocity (flow rate in gallons per minute or liters per second) significantly higher than gravity flow. This system is more water efficient than a tank type and can be installed into the same fittings as the latter. However it costs 10% less than the new 3″ (75 mm) gravity flapper equipped tank-type toilets. Pressure assist toilets are used in both private [single and multiple and lodging] bathrooms as well as light commercial installations [offices, etc.] They hardly ever clog and so require less maintenance.
“Automatic flush” refers to a triggering mechanism, rather than a water propulsion mechanism, although is usually implemented together with direct flush systems. Auto flush systems, as the name suggests, flush automatically once the user has left. Typically, an override button is provided if the user wishes to trigger flushing earlier. In retrofit installations a flushometer can be replaced with a self-contained battery operated machine vision system that actuates a solenoid when a user departs. There are two main kinds of machine vision systems used for sensor operated flush: passive; and active. Passive systems, such as Passive infrared (PIR), see the body of the user by electromagnetic energy that is received by the sensor. Active vision systems provide a source of electromagnetic energy (radar, infrared, or the like) and see reflected energy from the target (e.g. the user of the fixture). Automatic flushing cisterns may also be of the siphonic pattern, where a siphon is activated once water fills the tank and begins to run through the siphon tube.
Toilets are used in almost all civilized countries in the world. One country that has excelled in toilet development is Japan. The Japanese have some of the most advanced toilet systems in the modern world. The toilets used in Japan can do almost everything except cook. Western-style toilets and urinals started to appear in Japan at the beginning of the 20th century, but only after World War II did their use become more widespread, due to the influence of the American occupation. In 1977, the sale of Western-style toilets exceeded the sale of traditional squat toilets in Japan. Based on toilets with a built-in bidet from Switzerland and the U.S., the world's largest sanitary equipment company, TOTO, introduced the Washlet in 1980. Japanese companies currently produce some of the most advanced, high-tech toilets in the world, as evidenced by a high-end wireless toilet control panel with 38 buttons.
The standard flush toilet used worldwide is known in Japan as a Western-style toilet. Western-style toilets, including high tech toilets, are now more common in Japanese homes than the traditional squat toilets, though some older apartments retain stickers on the toilet or in its room illustrating the proper way to use it for urination and defecation. While most public facilities such as schools, temples, and train stations are often equipped with only squat toilets, in their own homes, Japanese people prefer being able to sit, especially older individuals for whom prolonged squatting is physically demanding or uncomfortable.
The modern toilet in Japan, commonly known in Japanese as Washlet or as warm-water cleaning toilet seat is likely the most advanced type of toilet worldwide, showing a dazzling array of features. The TOTO product Washlet Zoe is listed in the Guinness Book of Records as the world's most sophisticated toilet with seven functions. However, as the model was introduced in 1997, it is now likely to be inferior to the latest model by Toto Neorest. As of 2002, almost half of all private homes in Japan have washlet style toilets, exceeding the number of households with a personal computer. While the toilet looks like a Western-style toilet at first glance, there are a number of additional features, such as blow dryer, seat heating, massage options, water jet adjustments, automatic lid opening, flushing after use, wireless control panels, heating and air conditioning for the room, et cetera, included either as part of the toilet or in the seat. These features can be accessed by a control panel that is either attached to one side of the seat or on a wall nearby, often transmitting the commands wirelessly to the toilet seat.
The most basic feature is the integrated bidet, a nozzle the size of a pencil that comes out from underneath the toilet seat and squirts water. It has two settings: one for the anus and one for the vulva. The former is called posterior wash, general use, or family cleaning, and the latter is known as feminine cleaning or feminine wash. At no point does the nozzle actually touch the body of the user. The nozzle is also self-cleaning and cleans itself before and after operation. The user can select to wash the anus or vulva by pressing the corresponding button on the control panel. Usually the same nozzle is used for both operations, but at a different position of the nozzle head, and using different openings in the nozzle to squirt water at a different angle to aim for the correct spot. Occasionally, two nozzles are used, each dedicated for one area. The control logic is also attached to a pressure switch in the toilet seat, and operates only if there is pressure on the seat, indicating that the seat is occupied. The very first models did not include this automatic switch-off. The pressure switch was added to avoid accidental use without a user sitting on the toilet.
The Apricot washer, one of the most high-tech toilets also provides the option to select the water pressure to adjust to the preferences of the user. By default, the vulva receives less pressure than the anus. Usually, the temperature of the water can also be adjusted. Researchers in Japan have found that a water temperature slightly higher than the body temperature is preferred by most customers, and 38° C. is considered best. The exact nozzle position can also often be adjusted forward or aft manually. High-end washlets also provide options for a vibrating and pulsating jet of water. The most advanced washlets can even mix the water jet with soap for an improved cleaning process.
The washlet can replace toilet paper completely, but many users opt to improve the hygiene in combination with the mechanical action of the toilet paper. This also depends on the cleaned region, and the cleaning of the vulva may not need toilet paper. Some people use toilet paper before washing, some after washing, some use only the bidet and others do not use the bidet at all and prefer to use toilet paper.
A second commonly found feature is a blow drier, often adjustable between 40° C. and 60° C. to dry the private regions after cleaning with the integrated bidet. Other features may include a heated seat, which may be adjustable from 30° C. to 40° C.; an automatic lid equipped with a proximity sensor, which opens and closes based on the location of the user; automatic flushing; automatic air deodorizing; and a germ-resistant surface. Some models specially designed for the elderly may include arm rests and devices that help the user to stand up after use. A soft close feature slows the toilet lid down while closing so the lid does not slam onto the seat, or in some models, the toilet lid will close automatically a certain time after flushing. The most recent introduction is the ozone deodorant system that can quickly eliminate the smell of waste. Also, the latest models store the times of the use of the toilet, and have a power saving mode that heats up the toilet seat only during times when the toilet is likely to be used based on the collected usage data. Some toilets also glow in the dark or may even have air conditioning for hot summer days. Another recent innovation is intelligent sensors that detect someone standing before the toilet and automatically raise the lid (if the person is facing away from the toilet) or the lid and seat together (if someone is facing the toilet).
Recently, researchers have added medical sensors into these toilets, which can measure the blood sugar based on the urine, and also measure the pulse, blood pressure, and the body fat content of the user. Other measurements are currently being researched. This data may automatically be sent to a doctor through a built-in internet-capable cellular telephone. However, these devices are still very rare in Japan, and their future commercial success is difficult to predict. A voice-operated toilet that understands verbal commands is under development.
TOTO is the largest producer of toilets, including washlets worldwide. Washlets and other toilet related products are also produced by Inax, NAIS, and Panasonic. The total market worldwide for high-tech toilets was about US$800 million in 1997. In the U.S. for example, sales are well below Japanese levels, even though the sales improved from 600 units per month in 2001 to 1000 units per month in 2003. In Europe, Toto sells only 5000 washlets annually. While most Europeans would probably regard the Japanese washlets as quite a curiosity, the number of such toilets being installed in Europe is actually on the rise. This is mainly for the special purpose of toilets for the handicapped. Depending on the type of disability, handicapped persons may have difficulties reaching their anus regions in order to clean themselves after toilet use. Hence, the introduction of toilets with a water jet cleaner and blow dryer saves these persons from the embarrassing need to ask somebody else for assistance with an inherently private procedure.
Another country that has Hi-Tech toilets is Switzerland. Switzerland actually has its own producer of shower toilets, with a history predating the washlet in Japan. Trade names are Geberit-O-Mat and Geberella, produced by Balena. These toilets are sold primarily for hospitals, private homes, and a few high-level restaurants, and may include similar features as the Japanese products. Although there are many advanced toilets being produced in the world today, there are non that have the unique odor removal system as in the present invention.